Cryogenic tank

ABSTRACT

An insulated tank for storage of liquids at low temperatures. The tank has an outer shell comprising a bottom, sidewalls, and roof, and an inner shell comprising at least a bottom and sidewalls, with or without an inner roof. The inner shell bottom is made of metal sheet or plate suspended from a plurality of spaced-apart supports resting on the bottom of the outer shell. The suspended inner shell bottom has a plurality of elongated corrugations of smoothly undulating contour with the valleys of the corrugations being between the supports, and a plurality of corrugations crossing and generally conforming to the smoothly undulating contour of said elongated corrugations. The corrugations accommodate the liquid load and contraction of the suspended inner shell bottom during low temperature use of the tank without substantial horizontal movement of said suspended bottom or its supports and without overstressing the metal sheet or plate of which the inner shell bottom is made. The tank also has insulating material beneath said suspended inner shell metal bottom, between the inner and outer sidewalls of the tank and beneath the roof.

United States Patent [72] Inventor LyleV. Larsen NapervilleJll. [21] AppLNo. 829,020 [22] Filed May29, 1969 [45] Patented Apr. 27, 1971 [73] Assignee Chicago Bridge & Iron Company OakBrook, Ill.

[54] CRYOGENICTANK 12 Claims, 12 Drawing Figs.

[52] U.S.Cl 220/10, 220/15 [51] 1nt.Cl B65d7/22 [50] FieldofSear-ch ..220/10,15, 9(A); l14/ 74(A); 6 2/45; ll/9(A) [56] References Cited UNITED STATES PATENTS 2,437,909 3/1948 Cooper.... ..(220/9(A)UX) 2,451,486 10/1948 Horton.... 220/15 2,563,118 8/1951 Jackson... 220/15X 2,702,458 2/1955 Delmar 220/15X 3,094,071 6/1963 Beckman..... 220/15 3,220,595 ll/1965 Edwards 220/9 FOREIGN PATENTS 668,208 8/1963 Canada 220/9 1,442,256 5/1966 France 1,170,842 11/1969 Great Britain ABSTRACT: An insulated tank for storage of liquids at low temperatures. The tank has an outer shell comprising a bottom, sidewalls, and roof, and an inner shell comprising at least a bottom and sidewalls, with or without an inner roof. The inner shell bottom is made of metal sheet or plate suspended from a plurality of spaced-apart supports resting on the bottom of the outer shell. The suspended inner shell bottom has a plurality of elongated corrugations of smoothly undulating contour with the valleys of the corrugations being between the supports, and a plurality of corrugations crossing and generally conforming to the smoothly undulating contour of said elongated corrugations. The corrugations accommodate the liquid load and contraction of the suspended inner shell bottom during low temperature use of the tank without substantial horizontal movement of said suspended bottom or its supports and without overstressing the metal sheet or plate of which the inner shell bottom is made. The tank also has insulating material beneath said suspended inner shell metal bottom, between the inner and outer sidewalls of the tank and beneath the roof.

PATENTED APR27 12m SHEET 2 BF 3 e m w W a M Z J 7% CRYOGENIC TANK This invention relates to the storage of liquids at low temperature. More particularly, this invention is concerned with a novel tank for storage of cold liquids, such as liquefied gases, at or slightly above atmospheric pressure.

Many materials which are gases at ambient temperature and pressure are more economically stored as liquids at or near ambient pressure when the volume is large. Some such materials are petroleum gas, natural gas, ammonia, oxygen, nitrogen, methane and ethane.

The conventional tank for storing large volumes of liquefied gases at or near ambient pressure utilizes an internal shell and an external shell with suitable insulation between the shells; the walls are cylindrical; the bottoms are fiat and the roofs are flat or domed. The inner cylindrical wall accommodates at liquid temperature the internal liquid loads and the external insulation loads. The outer cylindrical wall contains the insulation at ambient temperature. The inner and outer flat bottoms support the liquid load but are, in turn, completely and directly supported by load-bearing insulation and a tank foundation, respectively. The inner roof supports the insulation and, in some instances, its own' weight and an internal or external pressure. The outer dome roof frequently supports its own weight, the weight of the inner roof and insulation and an internal or external pressure.

The physical requirements for the inner shell materials are considerably more stringent than for the outer shell materials because the inner shell must safely accommodate the forces imposed upon it at the temperature of the liquefied gas while the outer shell is at basically ambient temperatures. Premium steel, alloy steel, stainless steel or aluminum are required for the inner shell at a substantially higher unit cost than the common tank steel for the outer shell. In addition, the thickness of the premium steel or alloy steel is frequently limited by the stringent physical requirements imposed upon it and this, in turn, limits the size of the tank that can be constructed.

Worthwhile economies have been realized in constructing large storage tanks for liquefied gases by supporting the inner bottom completely and directly on load-bearing insulation and by supporting the inner roof and its insulation from the outer roof because this permitted the use of nominal inner roof and bottom thicknesses of three-sixteenths inch or one-fourth inch. Effective supporting of the inner cylindrical wall by the outer cylindrical wall could also produce very worthwhile economies and permit larger tanks to be constructed.

However, contraction and expansion of the inner cylindrical wall and the inner bottom, as the tank cycles between ambient temperature (for the construction and empty condition) and the temperature required for storing the liquefied gas at ambient pressure, has made this impractical with the conventional construction. The inner wall, during cooling, shrinks away from the outer wall and the support initially provided by the outer wall is lost.

Attempts have been made to construct inner shells that can be maintained at a fixed position relative to the outer shell and, thereby, utilize it for structural support. Unfortunately, these inner shells have been either extremely expensive materials (such as invar), severely deformed thin metal susceptible to cyclic fatigue or thin plastic materials susceptible to damage and leakage. All have required complete and direct support by relatively expensive loadbearing insulation for the walls, as well as the bottom, and their use has been largely experimental. A typical load-bearing insulation would cost $2.40 per cubic foot in place. as compared with 27 per cubic foot for the nonload-bearing t e of insulation used for the walls of large storage tanks for liquefied gas.

bottom is made of metal sheet or plate suspended from a plurality of spaced-apart supports resting on the bottom of the outer shell. The suspended inner shell bottom has a plurality of elongated corrugations of smoothly undulating contour with the valleys of the corrugations being between the supports, and a plurality of corrugations crossing and generally conforming to the smoothly undulating contour of said elongated corrugations. The corrugations accommodate the liquid load and contraction of the suspended inner shell bottom during low temperature use of the tank without substantial horizontal movement of said suspended bottom or its supports and without overstressing the metal sheet or plate of which the inner shell bottom is made.

The tank also has insulating material beneath said suspended inner shell metal bottom, between the inner and outer sidewalls of the tank and beneath the roof. Insulation of the roof can be effected in a number of ways. The roof can comprise part of the outer shell and have insulation either on the outside or the inside thereof. In another arrangement, a roof of uninsulated metal plate can be supported by the outer shell sidewalls and an insulated ceiling suspended therefrom into the periphery of the inner shell wall. In another arrangement, a floating insulating membrane can be placed in the tank and used alone to insulate the upper surface of liquid stored therein, with or without other insulation in the roof.

- The invention will be described further in conjunction with the attached drawings in which:

FIG. I is a vertical partial sectional view of a storage tank for liquefied gases or other liquids to be stored at low temperatures. The tank is essentially rectangular in horizontal section and has exterior walls supported by an earthen dike:

FIG. 2 is an enlarged vertical sectional view of a bottom portion of the tank of FIG. 1;

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 2 and shows U-shaped troughlike corrugations in the inner shell bottom;

FIG. 4 is a horizontal sectional view of a cylindrical tank in which the inner bottom has radial corrugations and a plurality of circular smoothly undulating corrugations spaced outwardly about the axis of the tank;

FIG. 5 is a vertical sectional view taken along the line 55 of FIG. 4;

FIG. 6 is a vertical sectional view similar to FIG. 5, but showing different supports for the inner shell bottom of the tank;

FIG. 7 is an elevational end view of a wooden support which can be used for supporting the inner shell bottom;

FIG. 8 is a side view of the support structure of FIG. 7;

FIG. 9 is an elevational end view of another support structure from which the inner shell bottom can be suspended;

FIG. llll is another support structure upon which the inner shell bottom of the tank can be suspended",

FIG. III shows another inner support structure upon which the inner shell bottom of the tank can be suspended; and

FIG. 12 is a side view of some of the supports of FIG. 6.

So far as is practical, the same or similar elements which appear in different views or FIGS. of the drawings shall be identified by the same reference numbers.

With reference to FIGS. 1 and 2, the tank of this drawing has a metal bottom I'll, which is generally rectangular, and opposing end walls ill joined to the bottom 10. The end walls 11, and opposing sidewalls, slope outwardly at an angle and are supported by earthen dike 12. Bottom 10, end walls Ill and sidewalls 18 can be made of carbon steel sheet or plate. A plurality of spaced-apart rows of supports 14 are positioned on the inside surface of outer bottom 10. Supports 14 are horizontally elongated, extend upwardly and have rounded top surfaces. The supports M are shown equally spaced apart and in parallel rows. They can, however, be spaced different distances apart as might be warranted in certain tank structures.

Inner shell bottom 15 of metal sheet or plate rests on the top curved surfaces of supports 14. The bottom 15 is thus suspended between adjacent supports 14. Inner shell bottom has a plurality of elongated corrugations 30 having a trough or valley portion 16 and an upper or ridge portion 17 all of which are shaped to have a smoothly undulating contour. The lower portions or valleys 16 are located between adjacent supports 14. The corrugations 30 can extend longitudinally up inner shell opposing sidewalls 18 to the top edges thereof. Furthermore, the two opposing inner shell end walls 31 are suspended from supports 19, similar to supports 14. The inner shell end walls contain corrugations 20 which are very similar to corrugations 30 and have a smoothly undulating contour with the corrugation valleys located between adjacent supports 19.

Although the tank as shown in FIG. 1 has the inner shell ends and sides provided with smoothly undulating corrugations, it is sometimes sufficient to provide the described corrugations only in the inner shell bottom.

Supports 14 and 19 can be made of insulating concrete. Granular insulation such as expanded vermiculite or perlite 21 can be placed between the supports 14 and 19 to insulate the bottom, end walls and sidewalls of the tank. Metal tabs 22 positioned in the top surface of supports 14 and 19 secure the inner shell bottom 15, inner end walls 31 and inner sidewalls 18 to such supports, so that expansion and contraction of the metal plates will be localized and restricted to the area between such stationary positions.

The supports 14, as shown in FIG. 3, are made in sections with the ends of adjacent sections positioned to provide a gap. The gap is filled with insulation 23 and provides a space for cross flexures or corrugations 24 in inner shell bottom 15. The bottom 15 of the inner shell is provided with a plurality of such corrugations 24 crossing, usually lateral or about perpendicular to the corrugations 30, and generally conforming to the smoothly undulating contour of corrugations 30. Furthermore, the flexures or corrugations 24 can extend longitudinally up the opposing inner shell walls 31 and can run essentially to the top of such opposing walls thereby providing for lateral expansion of such walls during temperature cycling.

Roof 25 of metal plate is supported at its periphery by vertical wall section 26 extending around all four outer sides of the rectangular tank. Additional support for roof 25 is provided internally by a plurality of columns 27. Tie bars 28 are joined at their lower ends to the inner shell bottom 15 and at their upper ends to roof 25 to strengthen the tank so it can withstand an internal pressure somewhat greater than ambient pressure. An insulated ceiling 29 is suspended from inside of roof 25 and extends about its periphery to the inside of inner shell walls 18 and 31 to thereby complete insulation of the internal space of the tank. A tank built according to the structure shown in FIGS. 1 to 3 will have minimal, if any, peripheral dimensional contraction of the inner shell bottom during temperature cycling and, as a result, there will be no inward pull of the tank walls as would be the case with a flat-bottomed inner shell. The suspended inner shell bottom 15 contributes to its own structural support and provides the noncontracting feature within acceptable and calculable stress levels.

The inner shell bottom 15 could be made of 3/16 inch thick aluminum plate suspended from supports 14 placed about 8 feet apart. The lower portion 16 of the corrugations could have about a 5 or 6 foot radius with the radius of the upper portion 17 going over the top of support 14 having a radius of about 4 feet. Flexures 24, as shown in FIG. 3, could be placed about 8 feet apart and be about 6 inches deep and about 6 inches wide. The curved structural flexure 24 would of course change radius of curvature along with the suspended corrugated bottom during cool-down and warm-up of the tank.

In constructing the tank, prefonned extruded flexures 24 could be installed in place and butt welded together end-toend. After that, the remaining inner shell portions could be installed. It would not be necessary, in many cases, to preform the smooth undulating corrugations if the metal plate used is sufficiently flexible to permit such shaping during installation such as if aluminum is used for the inner shell bottom.

The noncontracting inner shell bottom 15 has essentially no lateral movement and vertical shortenings due to temperature cycling are readily taken care of around the tank perimeter. The support system for the suspended bottom accommodates the load from the roof and the stored liquefied gas load and adequately distributes upward load from internal pressure even when the tank is empty. The support system remains essentially stationary with no appreciable lateral movement. Although the structure of FIGS. 1 to 3 shows the insulation between the inner and outer shells open at the top to the vapor space of the tank, this area could be sealed off as desired and gas pressure thereby avoided from being applied beneath the inner shell bottom.

FIGS. 4 and 5 illustrate the application of the invention to a cylindrical tank. The cylindrical tank has an outer shell flat circular metal bottom 40 from which outer cylindrical shell wall 41 extends upwardly to support a roof, not shown, thus forming a fully enclosed storage space. The tank has an inner shell composed of bottom 42 and vertical cylindrical wall 43. The inner shell bottom 42 has a series of progressively larger circular smoothly undulating corrugations 46, 47 and 50. Central support 44, axially positioned on the outer bottom 40 of the tank, together with the first circularly positioned series of supports 45 provide the means by which the first circular corrugation 46 in the inner shell bottom is suspended. The next consecutive circular corrugation 47 is suspended between the circularly positioned series of supports 45 and 48. Supports 45 and 48 are formed of arced metal tubing with the lower ends thereof joined to, or embedded in, base portion 49 such as of precast concrete. Supports 45 and 48 are spaced apart from one another in a consecutive manner to form a circular arrangement axially located with respect to the center of the tank. The number of such supports used will depend upon the size of the tank and the material used for its construction.

The outermost circular smoothly undulating corrugation 50 is supported on its inside by supports 48 while its outer area is arced upwardly to join with the vertical inner shell wall 43. The inner shell wall 43 is supported around its bottom edge by a series of rods 51 embedded in circular base 52.

The smoothly undulating circular corrugations 46, 47, and 50 are similar to corrugations 15 used in the rectangular tank of FIG. 1, except that they are not arranged in parallel fashion as in that tank but in circular arrangement as shown in FIG. 4.

In addition to having the circularly positioned smoothly undulating corrugations, the cylindrical tank of FIGS. 4 and 5 has at least the inner shell bottom corrugated radially intermittently or continuously in order that tangential expansion of the bottom can be achieved without substantially changing the overall external dimensions and periphery of the tank. The particular tank of FIG. 4 has the entire bottom radially corrugated. The number of radial corrugations in circular corrugation 46 will depend on the size of the tank and the width of circular corrugations 46. However, the number of radial corrugations can increase going from the inner circular corrugation 46 to the next adjacent circular corrugation 47 and can further increase from it to the outer circular corrugation 50 in order to accommodate the greater expansion involved as the distance from the center of the tank increases. Although FIG. 4 shows the number of radial corrugations increasing with each circular corrugation, this may not be necessary in all tanks and it may be sufficient under various operating conditions to continue the same number of radial corrugations for two or more circular corrugations. The radial corrugations in the inner shell bottom are advisably extended upwardly into, and constitute an integral part of, the inner shell vertical cylindrical wall 43. Such corrugations 56 permit expansion and contraction of the inner shell wall without significantly changing the diameter or circumferential dimensions of the tank. The corrugations 56 can extend continuously in vertical position around the entire wall or they can be placed intermittently in sufficient number and depth to achieve the desired result. Insulation 57 is placed between the bottoms and sidewalls of the inner and outer shells to provide necessary insulation.

FIG. 6 illustrates alternative supporting structures for the inner shell bottom of tanks as described in FIGS. I to 5. Thus, as shown in FIGS. 6 and 12, support 60 has a column portion 61 and a wider base portion 62. Extending upwardly from column portion 61 are two rods 63 which support an arced rod 64 from which corrugated bottom 65 is suspended.

FIG. 6 shows another support structure having a base 66 from which rods 67 project upwardly to support arcuately bent rod 68 upon which the corrugated bottom 65 rests. Instead of using rods 64 and 68 an elongated plate slightly arced can be used to suspend inner shell bottom 65. Similarly, the outermost support has a base 70 and a column portion 69 from which rod 71 extends to support the outer periphery of the inner shell bottom 65 as well as the wall of the inner shell.

A broad variety of different support structures can be used for suspending the inner shell bottom besides those already described in conjunction with FIGS. 1 to 6 and 12. Thus, as shown in FIGS. 7 and 8, a series of three woodboards 80 placed in edge-to-edge vertical arrangement with a lower horizontal spacer woodboard 81 and an upper horizontal spacer woodboard 82 between the next similar group of boards provides a suitable support for the bottom. The vtop of such support structure is arced 83 to mate with that portion of the smoothly undulating corrugation of the inner shell bottom which it supports. In addition, the tip edges of the boards 80 are rounded off in order to receive and support the crossflexures or corrugations. This type of structure is particularly useful since wood is inexpensive and has good insulating qualities.

FIG. 9 shows another support system in which a series of three boards 85 are positioned vertically in edge-to-edge arrangement and are held together by vertical boards 86 which alsofunction as spacers to keep adjacent similar columns of boards spaced apart. The top of such support system is furthen'nore arced 88 to provide good supporting contact from which the inner shell bottom can be suspended.

FIG. illustrates still another support structure for the inner shell bottom. Boards 90 and 91 intersect near the top and are joined at the bottom to the ends of horizontal board 92. The top edges of boards 90 and 91 are smoothly arced 93 to support a portion of the inner shell bottom plate.

The support structure of FIG. 11 shows a plurality of concrete members 95 having a wider upper portion 96 with the top surfaces thereof preshaped into corrugations for receiving the corrugations 97 of the inner shell bottom. The supports 95 can be placed in side-by-side position, either in parallel rows for use in a rectangular tank, or arranged circularly for use in a cylinder tank with radial corrugations in the inner shell bottom. The space 97 can be filled with suitable insulation if desired.

Although the invention has been described with particularity for use in storing liquefied gases, the tanks of this invention are also useful for storing normally liquid materials that are stored at higher or lower temperatures than ambient temperature. Also, the tanks can be used as ship tanks such as elongated corrugations of smoothly undulating contour with their valleys being between said supports and a plurality of second corrugations crossing, and generally conforming to the smoothly undulating contour of, the elongated corrugations,

said corrugations accommodating the liquid loading and contraction of said suspended bottom during low temperature use of the tank without substantial horizontal movement of said suspended bottom or its supports and without overstressing said metal sheet or plate, and

insulating material beneath said suspended inner shell metal bottom.

2. A storage tank according to claim 1 in which the second corrugations cross the first corrugations about perpendicularly.

3. A storage tank according to claim 1 in which the top surface of the horizontally elongated supports is rounded and the metal plate resting thereon follows the contour of the top surface.

4. A storage tank according to claim 1 in which the supports have gaps in which the second corrugations loosely depend.

5. A storage tank according to claim 1 in which the inner shell bottom is rectangular and the first corrugations are parallel to two opposing sides and the second corrugations are parallel to the two other opposing sides.

6. A storage tank according to claim 5 in which the sidewalls of the tank slope outwardly, the first corrugations run longitudinally upward from the bottom as part of two opposing sides, and the second corrugations ru n longitudinally upward from the bottom as part of the other two opposing sides.

7. A storage tank according to claim 1 in which the bottom is circular and the walls are cylindrical, the first corrugations are circularly arranged concentric with the axis of the bottom and the second corrugations are radially positioned.

8. A storage tank according to claim 7 in which the cylindrical wall has vertical corrugations.

9. A storage tank according to claim 1 in which the supports are metal rod having an arcuate top conforming to the contour of the inner shell metal bottom where they contact the bottom.

10. A storage tank according to claim I in which the supports are precast concrete having an arcuate top surface conforming to the contour of the inner shell metal bottom where they contact the bottom.

11. A storage tank according to claim 1 in which the supports are wooden and have an arcuate top surface conforming to the contour of the inner shell metal bottom where they contact the bottom.

12. In an insulated storage tank for low temperature liquids having an outer shell comprising a bottom, sidewalls and roof and an inner shell comprising at least a bottom and sidewalls, the improvements comprising:

an inner shell bottom of metal plate suspended from a plurality of spaced apart rows of supports resting on the bottom of the outer shell, each metal plate portion suspended between adjacent rows being in the fonn of an elongated corrugation or valley of smoothly undulating contour and substantially uniform depth, said corrugation being sufficiently deep to withstand contraction of the plate during low temperature use of the tank without horizontal displacement or movement of the plate on the elongated supports or the supports themselves, means connecting the metal plate to the elongated supports, a plurality of elongated flexures crossing the corrugations in the inner shell bottom metal plate, and having a longitudinal undulating contour corresponding to the corrugations in the inner shell bottom metal plate, and

insulating material between the rows of elongated supports and beneath the inner shell metal bottom. 

2. A storage tank according to claim 1 in which the second corrugations cross the first corrugations about perpendicularly.
 3. A storage tank according to claim 1 in which the top surface of the horizontally elongated supports is rounded and the metal plate resting thereon follows the contour of the top surface.
 4. A storage tank according to claim 1 in which the supports have gaps in which the second corrugations loosely depend.
 5. A storage tank according to claim 1 in which the inner shell bottom is rectangular and the first corrugations are parallel to two opposing sides and the second corrugations are parallel to the two other opposing sides.
 6. A storage tank according to claim 5 in which the sidewalls of the tank slope outwardly, the first corrugations run longitudinally upward from the bottom as part of two opposing sides, and the second corrugations run longitudinally upward from the bottom as part of the other two opposing sides.
 7. A storage tank according to claim 1 in which the bottom is circular and the walls are cylindrical, the first corrugations are circularly arranged concentric with the axis of the bottom and the second corrugations are radially positioned.
 8. A storage tank according to claim 7 in which the cylindrical wall has vertical corrugations.
 9. A storage tank according to claim 1 in which the supports are metal rod having an arcuate top conforming to the contour of the inner shell metal bottom where they contact the bottom.
 10. A storage tank according to claim 1 in which the supports are precast concrete having an arcuate top surface conforming to the contour of the inner shell metal bottom where they contact the bottom.
 11. A storage tank according to claim 1 in which the supports are wooden and have an arcuate top surface conforming to the contour of the inner shell metal bottom where they contact the bottom.
 12. In an insulated storage tank for low temperature liquids having an outer shell comprising a bottom, sidewalls and roof and an inner shell comprising at least a bottom and sidewalls, the improvements comprising: an inner shell bottom of metal plate suspended from a plurality of spaced apart rows of supports resting on the bottom of the outer shell, each metal plate portion suspended between adjacent rows being in the form of an elongated corrugation or valley of smoothly undulating contour and substantially uniform depth, said corrugation being sufficiently deep to withstand contraction of the plate during low temperature use of the tank without horizontal displacement or movement of the plate on the elongated supports or the supports themselves, means connecting the metal plate to the elongated supports, a plurality of elongated flexures crossing the corrugations in the inner shell bottom metal plate, and having a longitudinal undulating contour corresponding to the corrugations in the inner shell bottom metal plate, and insulating material between the rows of elongated supports and beneath the inner shell metal bottom. 